Locked antifriction bearing

ABSTRACT

The invention concerns a locked antifriction bearing, for control wheel, comprising an outer part ( 1 ) and an inner part ( 8 ), one being rotating and the other non-rotating through at least a row of rolling elements ( 12 ) arranged between said rotating and non-rotating parts, said device further comprising means for detecting rotation parameters and means for braking ( 33 ) the rotating part. The braking means comprises an axial stack of discs maintained in frictional contact through at least a disc angularly secured to the non-rotating part and at least a disc integral with the rotating part. The braking means comprises at least an elastic washer ( 38 ) for providing axially prestressed mutual contact of the friction surfaces of the discs.

[0001] The present invention relates to the field of instrumentedassemblies of the kind for control or operating wheels used, forexample, to steer motor vehicles, handling vehicles or civil engineeringworks vehicles or any other type of vehicle or machine requiring asteering wheel.

[0002] In the conventional way, a control wheel is connected to a shaft,for example a steering column shaft, which, depending on the type ofsteering used, either directly turns the steering mechanism in the caseof mechanical steering, actuates hydraulic pressure distributors in thecase of hydraulic steering or, finally, in the case of electricsteering, actuates the encoderring of a sensor delivering a signal tothe electric control motor, various combinations of these types beingpossible.

[0003] In the case of purely electrical steering, which is increasinglycommonly in use on handling vehicles such as fork lift trucks. A systemdetecting the rotation of the wheel, which may or may not beincorporated into the bearings, delivers, via a cable, a signalrepresentative of the turning of the wheel to the device for steeringthe wheels of the vehicle. As the wheel is mounted on its support by oneor more antifriction bearings and is not connected to mechanicaltorque-transmitting systems, the wheel can be turned with an extremelylow resistive torque. Often added to this is a wheel-braking systemintended to generate therein a resistive torque so as to encourageprecision and driveability in the driving of the vehicle. A device ofthis type is described, for example, in document DE-A-195 10 717.

[0004] This device does, however, exhibit certain disadvantages amongwhich we shall take note first of all of the relatively great axial bulkand the relatively high cost which are due to the presence of twoantifriction bearings in the continuation of which is arranged a brakingsystem employing a coil spring which presses a conical friction pieceinto a cup which also has a conical friction surface. The frictionaltorque developed by such a device is relatively low and the wear is highbecause of the small friction surfaces. Furthermore, the braking systemalters the operating play in the bearings.

[0005] Document FR-A-2 782 970 discloses a control wheel mounted on aninstrumented antifriction bearing and to which is added a brakingsystem, the rotating part of which is supported by the rotating innerring of the antifriction bearing and rubs against the end wall of ahousing. However, in this type of device, the antifriction bearing isnot mounted on a shaft and the diametral bulk of the bearing and of thedevice is great.

[0006] The invention proposes to overcome the disadvantages of thedevices of the prior art.

[0007] The invention proposes an economical and radially unbulky device.

[0008] The braked antifriction bearing device, according to one aspectof the invention, is of the kind intended for a control wheel. Thedevice comprises an outer part and an inner part, one being rotating andthe other non-rotating, a row of rolling elements which are arrangedbetween said rotating and non-rotating parts. Said device furthercomprises a means of detecting rotation parameters and a means ofbraking the rotating part. The braking means comprises a plurality ofdisks kept in frictional contact by at least one axially elasticelement. This yields a radially compact device which is simple tomanufacture and the braking characteristics of which are easilyadjustable. The disks may form an axial stack.

[0009] As a preference, the braking means comprises at least one disksecured axially to the non-rotating part and at least one disk securedangularly to the rotating part.

[0010] As a preference, the braking means comprises at least one elasticwasher which serves to ensure mutual contact with axial preload betweenthe friction surfaces of the disks.

[0011] In one embodiment, at least one of the disks of the braking meansis angularly connected to the corresponding part which supports it bymeans of a lug projecting into a slot.

[0012] In one embodiment, the braking means is in the form of an annularcartridge the two axial ends of which comprise a lateral element ofL-shaped cross section.

[0013] In one embodiment, the braking means is arranged radially betweenthe outer and inner parts and is arranged axially, at least in part, inthe axial continuation of the rolling elements and near the latter.

[0014] In one embodiment, the bearing device comprises two rings, onesecured to the rotating part and the other secured to the non-rotatingpart and between which the rolling elements are arranged.

[0015] In one embodiment, the means of detecting rotation parameterscomprises a sensor secured to the non-rotating ring and an encodersecured to the rotating ring.

[0016] In one embodiment, the sensor comprises a connection outputpassing through the non-rotating part.

[0017] In one embodiment, the non-rotating part comprises a tubularportion and a radial portion which is provided with means of attachingthe device to a support.

[0018] In one embodiment, the rotating part comprises a tubular portionand a radial portion which is provided with means of attaching a wheelto the device.

[0019] This braked bearing device can be fitted and mounted easily atnumerous possible locations on a vehicle or on a machine, for example ona dashboard, via the housing which acts as a support. Just a few screwsare needed to fix the device by means of the housing.

[0020] The present invention will be better understood and otheradvantages will become apparent from reading the detailed description ofa few embodiments taken by way of entirely nonlimiting examples andillustrated by the appended drawings, in which:

[0021]FIG. 1 is a view in axial section of a bearing device; and

[0022]FIG. 2 is a view in section on II-II of FIG. 1 of the bearingdevice.

[0023] As can be seen in the figures, the antifriction bearing devicecomprises an outer element 1 of annular shape, with an L-shaped halfsection, with a tubular portion 2 and a radial portion 3 extending atone end of the tubular portion outward. The radial portion 3 is providedwith a plurality of fixing holes 4 able to take screws with a view tofixing to a fixed structure, not depicted. The tubular portion 2 isprovided with two notches forming slots 5 extending from the free end ofsaid tubular portion 2 and situated opposite the radial portion 3. Theslots 5 are of rectangular shape, their length being aligned with theaxis referenced 6 on which the outer element 1 is centered. The outerelement 1 may be made of pressed or bent sheet metal. A cap 7, forexample made of synthetic material, with the shape of a disk, closes thefree end of the tubular portion 2 at which the slots 5 open, beingpush-fitted into its bore.

[0024] The antifriction bearing device also comprises an inner element8, also centered on the axis 6, of annular shape and U-shaped section,exhibiting a tubular portion 9 one end of which is closed off by aradial portion 10. A plurality of holes 11 are provided through thetubular portion 10 to take screws, not depicted, for example intendedfor fixing an operating wheel, also not depicted. The inner element 8may also be made of pressed sheet metal. Arranged between the outer 1and inner 8 elements is a row of rolling elements 12 which are held by acage 13.

[0025] In the alternative form illustrated in the figures, the rollingelements 12 are arranged between outer 14 and inner 15 rings. However,provision could be made for the rolling elements to be in direct contactwith the outer 3 and inner 8 elements via raceways formed on said outerand inner elements.

[0026] The outer ring 14 is push-fitted into the bore 2 a of the tubularportion 2 of the outer element 1 and is provided with a raceway 16 forthe rolling elements 12. The inner ring 15 is push-fitted onto the outersurface 9 a of the tubular portion 9 of the inner element 8 and isprovided with a raceway 17 for the rolling elements 12. The outer ring14 is also provided with two symmetric grooves 18 and 19 formed on itsbore, one on each side of the raceway 16. Fixed into the groove 18 is asealing member 20 which rubs against a bearing surface of the inner ring15. Fixed into the groove 19 is a sensor unit referenced 21 in itsentirety.

[0027] In the example illustrated, the sensor unit 21 comprises twodetection elements 22, 23, arranged diametrically opposed and eachembedded in a synthetic material forming a central part 24 of the sensorunit 21. The sensor unit 21 is fixed on the front face of the outer ring14 by means of a fixing support 25 inserted between the ring 14 and thesensor unit 21, both on the radial parts and on the circumferentialparts and a free end of which is bent into the groove 19.

[0028] A cylindrical annular portion 24 a is inserted partially into thebore of the non-rotating ring 14 more or less in the region of thegroove 19 so that the detection elements 22, 23 can be arranged partlybetween the two rings 14 and 15. An external protective plate 26 is alsofixed to the outside of the sensor unit 21 by crimping performed byfolding the other free end 25 a of the support 25 onto the periphery ofthe external protective plate 26.

[0029] The sensor unit 21 further comprises two wire terminals 27 and28, which are associated respectively with the detection elements 22 and23 and formed by an outgrowth of the synthetic material of the centralpart 24 for fixing the end of a cable 29, 30 by means of which a signalemitted can be passed onto an electric signal processing and operatingunit, not depicted in the figures. The wire terminals 27, 28 of thesensor unit 21 each project through a slot 5 of the tubular portion 2 ofthe outer element 1, being in contact with the end walls of said slots5.

[0030] The two detection elements 22, 23 each collaborate with a singleencoder ring 31 mounted facing the sensor unit 21 on the externalcylindrical surface of the rotating ring 15, so as to be driven inrotation by the latter.

[0031] The encoder ring 31 is mounted by means of a support 32 which ishoused in part between the rings 14 and 15. The support 31, of annularshape with T-shaped cross section, is push-fitted onto the outercylindrical surface of the rotating ring 15 and butts against a frontalsurface thereof. A portion of the encoder ring 31 thus lies between therings 14 and 15 and a portion projects outward. Most of the exteriorcylindrical surface of the encoder ring 31 lies facing the two detectionelements 22, 23, with a small gap.

[0032] An antifriction bearing is thus formed by the rolling elements 12and the rings 14 and 15. One or more sealing gaskets, one or moreencoders, one or more sensors, etc. may be added to this antifrictionbearing.

[0033] A braking member 33 is also arranged between the exterior surface9 a of the tubular portion 9 of the inner element 8 and the bore 2 a ofthe tubular portion 2 of the outer element 1. The braking member 33 isarranged in the axial continuation of the antifriction bearing equippedwith its system for detecting the rotation parameters and is situatedaxially between the free end of the tubular portion 9 of the innerelement 8 and the plate 26 protecting the sensor unit 21. Moregenerally, the braking member 33 is bounded axially by the cap 7,because provision could be made for it to project axially beyond thefree end of the tubular portion 9 toward said cap 7.

[0034] The braking member 33 comprises a rotating part 33 a formed oftwo elements 34, 35 of similar form and each comprising a tubular axialportion 34 a, 35 a and a radial portion 34 b, 35 b in the form of adisk. The free ends of the tubular portions 34 a, 35 a are mounted incontact with one another so that the elements 34 and 35 form a rotatingpart 33 a with a U-shaped cross section push-fitted onto the exteriorsurface 9 a of the tubular portion 9.

[0035] The non-rotating part 33 b of the braking member 33 comprises twometal disks 36 and 37 arranged axially between the radial portions 34 band 35 b of the rotating part 33 a. Arranged between the disks 36 and 37is an axially elastic washer 38. A friction lining or disk 39 isinserted axially between the disk 36 and the disk-shaped radial portion34 b. This friction lining or disk is made of a material with a highcoefficient of friction with respect to the fixed disks 41 and theradial portion 34 b. In the case of a lining, it is preferably bonded tothe disk 41 and rubs against the radial portion 34 b. The same is truefor the friction lining 40, the disk 37 and the radial portion 35 b.

[0036] The disks 36 and 37 each comprise two lugs 41, 42 projectingradially outward, diametrally opposed and arranged each one in a slot 5of the tubular portion 2 of the outer element 1.

[0037] In operation, the disks 36 and 37 are angularly secured to theouter element 1 because of the presence of the lugs 41, 42 which thusprevents any angular displacement with respect to the slots 5. The disks36, 37 are therefore fixed while the lateral elements 34, 35 can turn.The frictional contact between the fixed disks and the rotating elementsby way of the friction linings or disks 39, 40 therefore creates aresistive torque.

[0038] The elastic washer 38 permanently maintains an axial forcetending to force the disks 41 and 42 apart and thus ensure that thefriction linings or disks 39 and 40 rub on the corresponding surfaces ofthe radial portions 34 b and 35 b of the rotating part 33 a of thebraking member 33.

[0039] The braking means is thus in the form of a compact cartridgearranged radially between the fixed outer element 1 and the rotatinginner element 8, in the axial continuation of and in close proximity tothe instrumented antifriction bearing.

[0040] The structure of such a braking means has numerous advantages.First of all, it is very compact. Further, its modular design makes thefrictional torque easy to alter simply by altering the number of disks,the number or type of elastic preloading washers, it being possible forthis to be performed without any significant variation in the axial bulkof the cartridge, given the thinness of the components.

[0041] The braking means can, in a small bulk, generate a highfrictional torque because of the number and magnitude of the surfaces infrictional contact.

[0042] The structure of the braking cartridge allows the preload to bepreset easily by construction or by assembly, and therefore allows thebraking torque to be calibrated.

[0043] All that is required is to determine the value of the gap neededbetween the two radial portions 34 b and 35 b, according to the desiredpreload.

[0044] This gap value is obtained easily when the two elements 34 and 35are mounted on the inner element 8. All that is required is for theextent to which these two elements are push-fitted together to beadjusted, or alternatively for the length of the tubular parts 34 a and35 a to be predefined so that the desired gap is obtained when the freeends of the two tubular portions come into contact with one another.

[0045] This braking torque will remain particularly stable over timeduring operation because of the very little wear due to the largefriction surfaces. The fact that the axial forces exerted on the wheelfixed to the inner element 8 do not in any way alter the braking torqueis another advantage of the invention.

[0046] Finally, such a braking cartridge device has absolutely noinfluence on the antifriction bearings and is not likely to alter theclearance or preload thereof.

[0047] The various functions, particularly the bearing function affordedby the rolling elements 12, the function of detecting rotationparameters afforded by the sensor unit 21 and the function of brakingafforded by the braking member 33 are performed by means arranged in anannular space bounded radially between the tubular portion 2 of theouter element 1 and the tubular portion 9 of the inner element 8 andbounded axially between the radial portion 34 a of the element 34 of thebraking member 33 and the frontal surface of the rings 14 and 15opposite the sensor unit 21.

[0048] The various elements can be mounted by push-fitting theantifriction bearing and the braking member 33 onto the inner element 8then by bringing the outer element 1 from right to left in FIG. 1,causing the outer ring 14 to be push-fitted into the bore 2 a, causingthe wire terminals 27 and 28 to be pass into the slots 5 and causing thelugs 41 and 42 also to pass into the same slots 5. The cap 7 is thenfixed onto the outer element 1.

[0049] It will be noted that the slots 5, of which in an alternativeform there may be a number different than 2, allow both the passage ofthe cables 28 and 29 and the angular securing of the non-rotating part33 b of the braking member 33 and of the outer element 1. The variouselements are all of simple shape. The antifriction bearing may be ofstandard and therefore very economical type. The braking member can bemanufactured from sheet metal parts which are also very economical.

[0050] In place of the wire terminals 27 and 28, it would be possible toimagine a connector originating directly from the sensor unit 21. Theelastic washer 38 constantly maintains an axial force which tends tomove the disks 41 and 42 apart, increasing the friction of the frictionlinings or disks 39 and 40 on the corresponding surfaces of the rotatingpart 33 a of the braking member 33.

[0051] Of course, it is possible to imagine reversing the arrangement ofthe braking member, with the friction linings and disks secured to theelements 34 and 35, or alternatively reversing by swapping the rotatingpart and the non-rotating part. It would even be possible to imagine arotating outer element 1 and an non-rotating inner element 8. If thediameter of the inner element is small, it can be made from a solidpiece, of the cylindrical rod type, of a metallic or synthetic material.In the latter instance, said inner element could be produced as onepiece with other parts.

[0052] This braked antifriction bearing is particularly simple andeconomical to produce. It is perfectly modular and it is possible, inthe same bulk, simply by changing the elastic washer 38, to obtain ahigher or lower braking torque. It is also possible to alter thematerial of the disks or of the friction linings to alter the resultingfrictional torque.

[0053] It is also possible very easily to adapt the number of disks orpreload washers to alter the braking torque without that considerablyaltering the axial bulk of the device. The resistive torque generated bythe braking device can be high for a small bulk. This torque isperfectly calibrated by design and is particularly stable over timebecause the small amount of wear of the member of the elements has verylittle influence on the resistive torque. The entire braked antifrictionbearing is in the form of a cartridge which is very unlikely to loseparts and which appropriately protects the most delicate elements.

[0054] In the examples illustrated, the sensor unit 21 is locatedbetween the rolling elements 12 and the braking member 33. It is ofcourse conceivable, without departing from the scope of the invention,to design a device in which the sensor unit is arranged on one side ofthe row of roiling elements 12 and the braking member is arrangedaxially on the other side of said row. In this case, the braking member33 is no longer axially adjacent to the sensor unit as in FIG. 1, but isaxially adjacent to the rolling elements 12.

[0055] Of course it would be possible to provide a cartridge in whichthe device for detecting rotation parameters was not mounted on thebearing rings but beside them, for example in direct contact with theouter 1 and inner 8 elements. Provision could be made for just onesingle detection element and one single wire terminal to be used.

1. A braked antifriction bearing device of the kind for a control wheel,comprising an outer part (1) and an inner part (8), one being rotatingand the other non-rotating, a row of rolling elements (12) which arearranged between said rotating and non-rotating parts, said devicefurther comprising a means of detecting rotation parameters and a means(33) of braking the rotating part, characterized in that the brakingmeans comprises a plurality of disks kept in frictional contact by atleast one axially elastic element.
 2. The device as claimed in claim 1,characterized in that the braking means comprises at least one disksecured axially to the non-rotating part and at least one disk securedangularly to the rotating part.
 3. The device as claimed in claim 1 or2, characterized in that the braking means comprises at least oneelastic washer (38) which serves to ensure mutual contact with axialpreload between the friction surfaces of the disks.
 4. The device asclaimed in any one of the preceding claims, characterized in that atleast one of the disks of the braking means is angularly connected tothe corresponding part which supports it by means of a lug (41)projecting into a slot (5).
 5. The device as claimed in any one of thepreceding claims, characterized in that the braking means is in the formof an annular cartridge the two axial ends of which comprise a lateralelement of L-shaped cross section exhibiting a radial portion and anaxial portion.
 6. The device as claimed in any one of the precedingclaims, characterized in that the braking means is arranged radiallybetween the outer (1) and inner (8) parts and is arranged axially, atleast in part, in the axial continuation of the rolling elements andnear the latter.
 7. The device as claimed in any one of the precedingclaims, characterized in that it comprises two rings (14, 15), onesecured to the rotating part and the other secured to the non-rotatingpart and between which the rolling elements are arranged.
 8. The deviceas claimed in claim 7, characterized in that the means of detectingrotation parameters comprises a sensor (21) secured to the non-rotatingring and an encoder (31) secured to the rotating ring.
 9. The device asclaimed in claim 8, characterized in that the sensor comprises aconnection output (27) passing through the non-rotating part.
 10. Thedevice as claimed in any one of the preceding claims, characterized inthat the non-rotating part comprises a tubular portion (2) and a radialportion (3) which is provided with means of attaching the device to asupport.
 11. The device as claimed in any one of the preceding claims,characterized in that the rotating part comprises a tubular portion (9)and a radial portion (10) provided with means of attaching a wheel tothe device.